The following stamps below were
issued in extremely small quantities, and only a small part of the stamps
printed were sold to the general public by the Riga Main Post Office. In some
cases they were sold at other major town offices. The rest were purchased
in bulk by dealers, who even managed to initiate the issue and manipulate the
sale. The background of these activities have come to light in very few
cases even up to this date. The stamps are marked with surcharges of
up to several 1000 % of the nominal values.

Because of these features individual stamps of such sets were hardly ever
used for franking ordinary mail - except for philatelic airmail and Zeppelin
covers - these stamps primarily were traded in complete sets in mint condition
or on covers heavily over franked. For many years these stamps were not
recognized by several international catalogues as genuine postage stamps.
(Copied from The Postal and Monetary History of
Latvia 1918-1945 by N. Jakimovs, V.Marcilger)